OpenFlow is widely known as a technique for intensively managing a plurality of communication units by one control device. In OpenFlow, an OpenFlow Controller (denoted as OFC below) controls one or more OpenFlow Switches (denoted as OFS below). In recent years, there are increasing demands that an OpenFlow network is managed by a plurality of OFCs in consideration of the number of OFSs controllable by OFCs or the installation locations of the OFSs.
Patent Literature 1 describes a load distribution system enabling loads on a controller to be distributed also in a combination between switches and controller not having their own load distribution function or a combination between switches and controller not having compatible load distribution function due to different manufacturers. In the load distribution system described in Patent Literature 1, a proxy is installed between switches and controllers, the proxy notifies connection with one switch to a plurality of controllers, determines a master controller for the switch, and transfers an inquiry message from the switch to only the one master controller.